Devices powered by an external power supply module of “DC pack” type are traditionally switched on or off using a mechanical switch such as a rocker switch or a push switch, which retain the position they are given until operated again by a user. These mechanical switches are chosen in order to offer interrupting capacity characteristics sufficient to avoid causing an electric arc, damaging and then gradually destroying the contacts at the opening of the circuit. Despite this, a mechanical switch has a limited operating life generally defined in number of cycles of opening and closing. For example, a mechanical rocker switch can have an average number of cycles of 25,000 openings and closings before there is a risk of harmful damage to its contacts.
An alternative consists in using a mechanical switch whose current characteristics are only a few tens of milliamperes and using this component in a control circuit for a MOSFET power transistor which will act as a high interrupting capacity switch capable of being crossed by a high load current.
These mechanical solutions have the advantage of disconnecting the powered item of equipment from the power supply rail and of guaranteeing the absence of residual current when a powered device is configured in an “off” or more precisely a “powered off” mode.
They nevertheless have disadvantages, notably:                the price of a mechanical solution is substantially higher than that of an electronic solution,        the gradual and inevitable wearing of the contacts,        the fact that it is impossible to control these switches using embedded software except by using a relay or bistable relay, but this solution appears unsuitable in the case of powering electronic devices, such as, for example, audiovisual programme receiver-decoders, or network gateways.        
The main advantages of mechanical rocker switches or mechanical push switches are their ease of use and the position memory effect, since, once positioned in “on” or “off” mode, they retain their position until operated again.
For the implementation of the memory effect, solutions exist which comprise a tact switch (also called a micro-switch) coupled to a MOSFET and to a control unit with microcontroller, having a non-volatile memory. The microcontroller in this case records the position of the power supply circuit (“on” or “off”). However, this solution requires restarting the entire system, after an unexpected disappearance of the power supply current, in order to define which state is stored in the memory and reconfigure the system to “off” mode, if necessary.
This solution requires an almost-permanent state of activation of the microcontroller in order to read the memory and monitor the state of the micro-switch, which results in an energy consumption which is non-negligible and disadvantageous with respect to the maximum values appearing in European Directive 1275/2008 relating to power consumption of equipment in standby mode.
In addition, and in the case of a mechanical solution, a request for a complete switching off cannot be made remotely (via a remote control) or by programming (on detection of an expiry of a timer or of a predefined event).
In addition to the additional cost it incurs, the mechanical switch appears more difficult to incorporate into a cosmetic “front face” of an item of equipment. A software-controlled solution resolves this type of problem, but on the other hand requires a disconnection and reconnection to the mains network in the event of malfunctioning related to a software “crash”.
The solutions mentioned all have disadvantages.